The present invention generally relates to the use of a novel air knife to help prevent solid particulates from blocking the entrance to a vessel. More specifically, the present invention is particularly useful for reducing blockage by solid chlorides removed from a titanium tetrachloride product gas by a cyclone or by some other gas/solids separation device, in processes for producing titanium tetrachloride.
The production of titanium tetrachloride (xe2x80x9cTiCl4xe2x80x9d) via the chlorination of titanium values in a titanium-containing starting material is generally known in the art. The production of TiCl4 is useful, for example, in the production of titanium metal or titanium dioxide (xe2x80x9cTiO2xe2x80x9d).
As is known in the art, TiCl4 can be produced by reacting chlorine gas with titanium-containing starting materials in a chlorinator. During this process, a solids-laden gas mixture comprised of the desired TiCl4 gas and residual solid chlorides is removed from the chlorinator, cooled, and conventionally is then transferred to a cyclone separator to remove the solids from the solids-laden gas mixture. The solids are then dumped into a suspension vessel, frequently referred to as a chlorinator sump, where the solids are mixed with water to form a suspension.
These removed solids are typically very warm upon entering the suspension vessel. The mixing of these hot solids with water in the suspension vessel results in a high humidity gas phase in the space above the suspension in the vessel, including the length of pipe that carries the cyclone dust from the cyclone to the suspension vessel. The cyclone dust contains metal chlorides, which are hygroscopic, and as such become sticky when entering the high humidity areas of the pipe that transfers the cyclone dust from the cyclone to the suspension vessel. The sticky solids gradually build up on the walls of the pipe until the pipe is completely plugged, stopping further discharge of solids from the cyclone. Clearing the blockage requires operation downtime to unclog and can be a safety hazard.
The present invention addresses the issues presented above by placing a novel air knife at or near the entrance to the suspension vessel. The cyclone dust passes through the air knife on its way to the suspension vessel. The novel air knife is circumferential. That is, the novel air knife injects a gas stream along the inside walls of the air knife. The gas stream is injected at a rate sufficient to reduce the buildup of hygroscopic cyclone dust on the walls of the air knife (and thus at the entrance to the chlorinator sump), so that the chlorinator sump can continue to receive solids from the cyclone, improving time-on-line and safety.
In one embodiment, the present invention is a novel air knife adapted to reduce hygroscopic solids from building up at the entrance to a suspension vessel enclosing a high-humidity environment. In a second embodiment, the present invention is a method for preventing hygroscopic solids from building up at the entrance to a suspension vessel enclosing a high-humidity environment.